Eiichiro Sakaguchi

Water Absorption Characteristics and Volume Changes of Milled and Brown Rice During Soaking

ABSTRACT The water absorption characteristics and volume changes of rice with various degrees of milling during soaking were measured at five temperatures (5–40°C). The measured data were fitted to the exact solution for the infinite plane sheet diffusion model, which is an exact solution for the diffusion equation. The measured results agreed well with the model. The effects of temperature and the degree of milling on the water absorption rate constant were investigated. Volume changes of samples were determined by measuring particle density and bulk density. An empirical equation relating the moisture content of the sample during soaking and at temperatures of 10–50°C to specific volume was derived. In addition, bulk density was related to the quadratic function of the moisture content of the sample during soaking.

Simultaneous Estimation of the Thermophysical Properties of Selected Liquid Dairy Products by a Transient Heat Flow Probe Method

The thermophysical properties of reconstituted whole milk, skim milk, and whey were measured at various temperatures and concentrations. A new method for the simultaneous determination of thermophysical properties using a modified version of current probe theory method was proposed. Two new correction coefficients were introduced, and using the values of these coefficients and an approximate solution of the heat conduction equation, the thermal conductivity and thermal diffusivity of each sample were determined. The specific heat of each sample was estimated from the definition of thermal diffusivity. These properties were expressed as a function of concentration and temperature.

Thin Layer Drying Model for Cooked Soybeans

The drying characteristics (changes in moisture content and volume of sample during drying) of cooked soybeans (boiled soybeans) were measured at selected operating conditions. The sample was dried by the two kinds of drying methods; the hot air drying method and the continuous vacuum drying method. From the observed relationship between the drying rate and moisture content of the sample, we estimated that the continuous vacuum drying process of the sample was composed of the two periods; the constant rate period and the falling rate period. The hot air drying process of the sample was in the falling rate period. In the constant rate period for the continuous vacuum drying (above 100 % d.b.), the moisture contents of the sample decreased with elapsed time and represented as a linear function of elapsed time. The falling rate period for the continuous vacuum drying (below 100 % d.b.) was in the first falling rate period, and the measured moisture contents of the sample agreed well with the values calculated from the exponential model. The Page equation could be used to estimate the changes in moisture content of the sample for the hot air drying process. An Arrhenius-type equation was used to relate the dying rate constant of the sample for each drying method and period to temperature. Volume changes of the sample during drying were determined by measuring particle density. An empirical equation relating the moisture content of the sample and temperature to specific volume was derived.

Simultaneous Estimation and Modeling of Thermophysical Properties of Big-Eyed Tuna and Pacific Cod

The thermophysical properties (thermal conductivity, thermal diffusivity, and specific heat) of big-eyed tuna and pacific cod were measured at various temperatures (5–50°C) by the modified version of current probe method. The optimal prediction models for these thermophysical properties were determined. The random model was applied to predict the thermal conductivity of seafood in a wide range of temperature and it provided the accurate predictions for the samples. The thermal diffusivities of the samples could be predicted by Martens’s equation. An additive relationship exists between the specific heat of the sample, the composition, and the specific heat of each component.

Hot Air Drying and Vacuum Drying Characteristics of Scarlet Runner Beans

Abstract The drying characteristics and volume changes of scarlet runner beans were measured under various conditions to obtain useful basic information for the optimum drying method and conditions. The sample was dried using two drying methods: hot air drying and vacuum drying. The measured changes in moisture content of the sample with the hot air drying process were in good agreement with the exact solution of the infinite plane sheet model. The estimated diffusion coefficients were 3.8×10 -7 -7.4×10 -7 (m 2 h -1) for hot air drying and were related to absolute temperature by an Arrhenius-type equation. The hull of the scarlet runner bean is hard and thick, and the drying rate of the sample was much slower than that of other beans. To establish an efficient drying method without the quality loss, the vacuum drying characteristics of the sample were measured at several levels for temperature and initial moisture content. For the vacuum drying process, an exponential model could be used to estimate the changes in moisture content of the sample. The values of diffusion coefficient for vacuum drying were approximately twice as much as the values of diffusion coefficient for hot air drying at the same temperature. The effects of drying method, temperature, and initial moisture content on the sample quality were investigated, and the optimum drying method and conditions for scarlet runner beans were proposed. Volumetric changes in the sample were determined by measuring particle density. The specific volume of the sample was represented as a linear function of moisture content.

Drying Characteristics of Japanese Yam (Dioscorea opposita Thunb.)

The drying characteristics (changes of mass (moisture content), volume, drying surface area, and surface and internal temperature of sample during drying) of Japanese yam (Dioscorea opposita Thunb.) were measured under various operating conditions (temperature, relative humidity, and absolute pressure (vacuum level)). Japanese yam was dried by two methods, hot air drying and continuous vacuum drying. The effects of temperature, relative humidity, and absolute pressure on the drying rate of the sample were investigated. The moisture content change of the sample was analyzed under two conditions, considering or not considering the drying surface area change. When surface area change is considered, two periods, the constant rate period and the falling rate period, existed in both hot air drying and vacuum drying of the sample. In each case, mathematical models to describe the changes of the moisture content were derived, and the measured data agreed well with the values calculated from the models. The effects of temperature, relative humidity, and vacuum level on the drying rate constant were investigated. The drying rate constants were related to the temperature and relative humidity for hot air drying, or the temperature and vacuum level for vacuum drying using empirical equations which are modified form an Arrhenius-type equation.

Discrete Element Analysis of Micro-mechanical Behaviour of a Grain Assembly in Constant Load Direct Shear

Two-dimensional shear box test using vinyl chloride cylinders and vinyl chloride elliptical cylinders and three-dimensional test using brown rice and nylon spheres were performed. The macroscopic shear behaviour of a brown rice assembly had similarities to an elliptical cylinder assembly. The results of two-dimensional discrete element (DE) simulation using circular particles and experiment using the cylinders were in good agreement with the macroscopic shear behaviour of the bulk. As a result of this validation microscopic shear behaviours were analyzed using the DE model. There was a good correlation between the shear force totaled normal force acting on the side wall of the upper box and the sum of contact force in the box. An average angle formed by a contact force vector between particles in the box was close to the simulated internal friction angle. The rotation of maximum principal stress axis in the bed during shearing was suggested by few sliding particles and rotation of principal axis of fabric tensor. The rotation of principal stress axis caused the development of induced anisotropy in the granular media.